β2 Adrenergic receptor agonists are recognized as effective drugs for the treatment of pulmonary diseases such as asthma and chronic obstructive pulmonary disease (including chronic bronchitis and emphysema). β2 Adrenergic receptor agonists are also useful for treating pre-term labor, and are potentially useful for treating neurological disorders and cardiac disorders. Commonly assigned U.S. Pat. Nos. 6,653,323 B2 and 6,670,376 B1 disclose the novel compound N-{2-[4-(3-phenyl-4-methoxyphenyl)aminophenyl]ethyl}-(R)-2-hydroxy-2-(8-hydroxy-2(1H)-quinolinon-5-yl)ethylamine,
as a potent β2 adrenergic receptor agonist. Compound 1 is alternatively referenced by the chemical name 8-hydroxy-5-((R)-1-hydroxy-2-{2-[4-(6-methoxybiphenyl-3-ylamino)-phenyl]ethylamino}ethyl)-1H-quinolin-2-one.
In order to purify and formulate medicinal compounds for use as therapeutic agents, it is advantageous to provide the compounds in crystalline form. No crystalline form of compound 1 or of a pharmaceutical salt thereof has been reported previously.